In a Conventional SAGD (Steam Assisted Gravity Drainage) configuration, a “dual well” process includes the horizontal drilling of two parallel wells one above the other. The upper well is dedicated to continuous steam injection and the lower well is for recovering reservoir fluids. The separation between the injector well and the producer well and the separation between the well pairs are a function of the reservoir and oil properties.
In a Single-Well SAGD (SW-SAGD) configuration, only one horizontal well is used for both injection and production. This configuration, under the same operating conditions as Conventional SAGD, suffers from excessive steam production at the facilities. An alternate configuration is to place vertical steam injectors above or between the horizontal extractors.
In a Triangle SAGD (TRI-SAGD) configuration, horizontal injectors are drilled halfway between the horizontal producers with the injectors positioned above the producers. TRI-SAGD is acknowledged to require the minimum number of wells for SAGD.
The THAI (Toe to Heel Air Injection) process is disclosed in Canadian Patent No. 2,176,639, by Petrobank Energy Ltd, a Calgary Canada Company. FIG. 1 shows how the THAI process works. In the THAI process air injection/ignition takes place from a vertical well 11. The arrows 12 show the injection of air. The air and fuel content combust forming a fire front 13. The fire front 13 heats up the cold crude and the reservoir fluids 15 (gas and liquids) are recovered from a horizontal leg 14A of an extraction well 14.
There is a need for an improved oil recovery process, one that increases extraction efficiency and uses less energy than conventional methods. The present invention provides such a solution.